What the FDA's review reveals about Pfizer's COVID-19 vaccine

Regulators discuss efficacy, side effects
Posted at 6:58 PM, Dec 08, 2020
and last updated 2020-12-08 22:37:00-05

SAN DIEGO (KGTV) — Regulators at the Food and Drug Administration said they found no red flags that would stand in the way of authorizing Pfizer’s COVID-19 vaccine on an emergency basis.

FDA scientists independently confirmed Pfizer’s claim that its vaccine is 95 percent effective after two doses and said they found no serious safety concerns, according to documents released Tuesday.

The FDA released the 53-page review ahead of a meeting this week by an outside group of vaccine experts that will advise the agency and vote on whether to recommend an emergency use authorization for the drug in people 16 and older. A San Diego doctor will be among the 30 voting members.

Government regulators examined the vaccine’s efficacy in subgroups and found it remained highly effective regardless of age, gender, race and risk factors. The vaccine scored 91 percent or better in nearly every way the agency sliced the data.

“The news is really outstandingly good in terms of efficacy,” said Dr. Christian Ramers of Family Health Centers of San Diego. “It’s kind of almost a dream come true to have something that's 90 percent efficacious. If you recall, the FDA was shooting for better than 50 percent.”

Among adults who were aged 65 or older and obese, one of the highest risk groups for severe COVID-19, the vaccine was 100 percent effective. That means no one who got the vaccine got sick, only volunteers in the placebo arm who got salt water.

Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, noted that most influenza vaccines are between 40 and 60 percent effective. “So getting 90 percent and above in some groups is just staggering,” he said.

Pfizer’s vaccine is administered in two doses staggered three weeks apart. The FDA’s review began providing protection after 10 days, and just one dose reduced cases by 52 percent.

That could spark discussion about how to allocate scarce doses in countries with limited access; however, Dr. Chin-Hong said there are too many unknowns to skip the second shot.

“We don't know how long that protection would last,” he said. “Given the history and experience with other vaccines, we know that you get a more durable level of antibodies after a second shot.”

The FDA also examined side effects in detail. Regulators found the majority of people who got the vaccine experienced some kind of mild to moderate side effect that resolved within a few days. A moderate side effect interferes with, but does not prevent, daily activity.

According to the data, 84 percent of recipients had a reaction at the injection site, 63 percent felt fatigue, 55 percent had a headache, 38 percent experienced muscle pain, 32 percent had chills, 23 percent had joint pain and 14 percent had a fever.

“These are things you expect from a vaccine. It actually means that it's working,” Dr. Ramers said. “That’s your immune system learning from that vaccine how to fight that bad virus.”

Because of the mechanics of how Pfizer’s mRNA vaccine trains the body to build an immune response, there is no way the vaccine can cause COVID-19, he noted. The vaccine does not contain actual virus or viral particles.

The FDA also looked for signs of any serious side effects in the trial of 44,000 volunteers. The agency noted there were four cases of temporary facial paralysis called Bell’s palsy in the vaccine group and none in the placebo group.

Despite the apparent imbalance, the FDA scientists noted the numbers were so small the cases could have been caused by something other than the vaccine. In a large group of people, a certain number of cases of Bell’s palsy are expected to occur because the disorder can be caused by several pathogens.

The number of cases in the vaccine group did not exceed what regulators call the background rate, meaning the number of cases that would be expected to occur in the general public.

Bell’s palsy is temporary and treatable. Actress Angelina Jolie announced in 2017 she experienced a bout of Bell’s palsy and fully recovered.